Liquid crystal display device

ABSTRACT

To provide a liquid crystal display device suitable for a thin film transistor which uses an oxide semiconductor. In a liquid crystal display device which includes a thin film transistor including an oxide semiconductor layer, a film having a function of attenuating the intensity of transmitting visible light is used as an interlayer film which covers at least the oxide semiconductor layer. As the film having a function of attenuating the intensity of transmitting visible light, a coloring layer can be used and a light-transmitting chromatic color resin layer is preferably used. An interlayer film which includes a light-transmitting chromatic color resin layer and a light-blocking layer may be formed in order that the light-blocking layer is used as a film having a function of attenuating the intensity of transmitting visible light.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a liquid crystal display device inwhich an oxide semiconductor is used and a manufacturing method thereof.

2. Description of the Related Art

As typically seen in a liquid crystal display device, a thin filmtransistor formed over a flat plate such as a glass substrate ismanufactured using amorphous silicon or polycrystalline silicon. A thinfilm transistor manufactured using amorphous silicon has low fieldeffect mobility, but can be formed over a large glass substrate. Incontrast, a thin film transistor manufactured using crystalline siliconhas high field effect mobility, but due to a crystallization step suchas laser annealing, such a transistor is not always suitable for beingformed over a large glass substrate.

In view of the foregoing, attention has been drawn to a technique bywhich a thin film transistor is manufactured using an oxidesemiconductor and such a transistor is applied to an electronic deviceor an optical device. For example, Patent Document 1 and Patent Document2 disclose a technique by which a thin film transistor is manufacturedusing zinc oxide or an In—Ga—Zn—O-based oxide semiconductor for an oxidesemiconductor film and such a transistor is used as a switching elementor the like of an image display device.

The field effect mobility of a thin film transistor that uses an oxidesemiconductor for a channel formation region is higher than that of athin film transistor that uses amorphous silicon. The oxidesemiconductor film can be formed by a sputtering method or the like at atemperature of 300° C. or less. Its manufacturing process is easier thanthat of a thin film transistor that uses polycrystalline silicon.

An oxide semiconductor is a transparent semiconductor which transmitslight in a visible wavelength range; accordingly, it is said that byusing the oxide semiconductor for a pixel of a display device, a higheraperture ratio can be obtained.

Such an oxide semiconductor is expected to be used for forming a thinfilm transistor on a glass substrate, a plastic substrate, or the like,and to be applied to a display device.

REFERENCE [Patent Document 1] Japanese Published Patent Application No.2007-123861 [Patent Document 2] Japanese Published Patent ApplicationNo. 2007-096055 SUMMARY OF THE INVENTION

Therefore, it is an object to provide a liquid crystal display devicesuitable for a thin film transistor that uses an oxide semiconductor.

In a liquid crystal display device which includes a thin film transistorincluding an oxide semiconductor layer, a film having a function ofattenuating the intensity of transmitting visible light is used as aninterlayer film which covers at least the oxide semiconductor layer. Thefilm having a function of attenuating the intensity of transmittingvisible light is a film having a transmittance of visible light lowerthan the oxide semiconductor layer. As the film having a function ofattenuating the intensity of transmitting visible light, a coloringlayer can be used and a light-transmitting chromatic color resin layeris preferably used. An interlayer film which includes alight-transmitting chromatic color resin layer and a light-blockinglayer may be formed in order that the light-blocking layer is used as afilm having a function of attenuating the intensity of transmittingvisible light.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as an interlayer film provided over a thin filmtransistor, the intensity of incident light on a semiconductor layer ofthe thin film transistor can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistor can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Chromatic colors are colors except achromatic colors such as black,gray, and white. The light-transmitting chromatic color resin layer isformed using a material which transmits only light of a chromatic colorwhich the material is colored in so as to serve as a color filter. As achromatic color, red, green, blue, or the like can be used.Alternatively, cyan, magenta, yellow, or the like may be used.“Transmitting only light of a chromatic color which a material iscolored in” means that light transmitted through the light-transmittingchromatic color resin layer has a peak at the wavelength of thechromatic color light.

The thickness of the light-transmitting chromatic color resin layer ispreferably controlled as appropriate and optimized in consideration ofthe relation between the concentration of the coloring material to beincluded and the transmittance, in order that the light-transmittingchromatic color resin layer functions as a color filter layer. In thecase where the interlayer film is formed of a plurality of thin films,if at least one layer thereof is a light-transmitting chromatic colorresin layer, the interlayer film can function as a color filter.

In the case where the thickness varies depending on the chromatic colorsor in the case where there is surface unevenness due to a thin filmtransistor, an insulating layer which transmits light in a visiblewavelength range (a so-called colorless, transparent insulating layer)may be stacked for planarization of the surface of the interlayer film.The planarization of the interlayer film enables favorable coverage by apixel electrode layer or a common electrode layer to be formed thereoverand uniform gap (thickness) of a liquid crystal layer, whereby thevisibility of the liquid crystal display device is increased and higherimage quality can be achieved.

When a light-blocking layer (black matrix) is used in the interlayerfilm provided over the thin film transistor, the light-blocking layercan block incident light on the semiconductor layer of the thin filmtransistor; accordingly, electric characteristics of the thin filmtransistor can be prevented from being varied due to photosensitivity ofthe oxide semiconductor and can be stabilized. Further, thelight-blocking layer can prevent light leakage to an adjacent pixel,which enables higher contrast and higher definition display. Therefore,high definition and high reliability of the liquid crystal displaydevice can be achieved.

In this specification, a substrate over which a thin film transistor, apixel electrode layer, a common electrode layer, and an interlayer filmare formed is called an element substrate (a first substrate), and asubstrate which is positioned opposite from the element substrate with aliquid crystal layer interposed therebetween is called a countersubstrate (a second substrate).

The light-blocking layer can be formed on either the counter substrateside or the element substrate side of the liquid crystal display device.Accordingly, contrast can be increased and the thin film transistor canbe stabilized more. In the case where the light-blocking layer is formedin a region corresponding to a thin film transistor (at least in aregion which overlaps with a semiconductor layer of a thin filmtransistor), electric characteristics of the thin film transistor can beprevented from being varied due to incident light from the countersubstrate. In the case of forming the light-blocking layer on thecounter substrate side, the light-blocking layer may be formed in aregion which corresponds to a thin film transistor with a liquid crystallayer interposed therebetween (at least in a region which overlaps witha semiconductor layer of a thin film transistor). In the case of formingthe light-blocking layer on the element substrate side, thelight-blocking layer may be formed directly on the thin film transistor(at least in a region which covers a semiconductor layer of the thinfilm transistor) or formed over the thin film transistor with aninsulating layer interposed therebetween.

In the case of providing the light-blocking layer also on the countersubstrate side, there is a case in which light from the elementsubstrate and light from the counter substrate to the semiconductorlayer of the thin film transistor can be blocked by a light-blockingwiring layer, electrode layer, or the like. Thus, the light-blockinglayer need not always be formed to cover the thin film transistor.

An embodiment of the invention disclosed in this specification includesa thin film transistor in which an oxide semiconductor layer overlappingwith a gate electrode layer serves as a channel formation region; apixel electrode layer electrically connected to the thin filmtransistor; an interlayer film provided between the thin film transistorand the pixel electrode layer; and a liquid crystal layer provided overthe thin film transistor, the pixel electrode layer, and the interlayerfilm, in which the interlayer film is a light-transmitting chromaticcolor resin layer which has a transmittance lower than the oxidesemiconductor layer, and in which the light-transmitting chromatic colorresin layer is provided so as to overlap with the pixel electrode layerand cover the oxide semiconductor layer.

Another embodiment of the invention disclosed in this specificationincludes a thin film transistor in which an oxide semiconductor layeroverlapping with a gate electrode layer serves as a channel formationregion; a pixel electrode layer electrically connected to the thin filmtransistor; an interlayer film provided between the thin film transistorand the pixel electrode layer; and a liquid crystal layer provided overthe thin film transistor, the pixel electrode layer, and the interlayerfilm, in which the interlayer film includes a light-blocking layer and alight-transmitting chromatic color resin layer which has a transmittancelower than the oxide semiconductor layer, in which the light-blockinglayer is provided so as to cover the oxide semiconductor layer, and inwhich the light-transmitting chromatic color resin layer is provided soas to overlap with the pixel electrode layer.

Note that ordinal numbers such as “first” and “second” in thisspecification are used for convenience. Therefore, they do not denotethe order of steps, the stacking order of layers, and particular nameswhich specify the invention.

In this specification, a semiconductor device refers to all types ofdevices which can function by utilizing semiconductor characteristics.An electro-optical device, a semiconductor circuit, and an electronicdevice are all included in the category of the semiconductor device.

In a liquid crystal display device which includes a thin film transistorformed by using an oxide semiconductor layer for a channel, aninterlayer film which covers at least the oxide semiconductor layer isformed using a material which attenuates the intensity of transmittingvisible light. Accordingly, operation characteristics of the thin filmtransistor can be stabilized without reduction in an aperture ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 illustrates a liquid crystal display device;

FIG. 2 illustrates a liquid crystal display device;

FIGS. 3A and 3B illustrate a liquid crystal display device;

FIGS. 4A and 4B illustrate a liquid crystal display device;

FIGS. 5A and 5B illustrate a liquid crystal display device;

FIGS. 6A and 6B illustrate a liquid crystal display device;

FIGS. 7A and 7B illustrate a liquid crystal display device;

FIGS. 8A to 8D each illustrate an electrode layer of a liquid crystaldisplay device;

FIGS. 9A and 9B illustrate a liquid crystal display device;

FIGS. 10A and 10B illustrate a liquid crystal display device;

FIGS. 11A and 11B illustrate a liquid crystal display device;

FIGS. 12A1, 12A2, and 12B illustrate liquid crystal display devices;

FIG. 13A is an external view illustrating an example of a televisiondevice and FIG. 13B is an external view illustrating an example of adigital photo frame;

FIGS. 14A and 14B are external views illustrating examples of gamemachines;

FIGS. 15A and 15B are external views illustrating examples of mobilephones;

FIG. 16 illustrates a liquid crystal display module;

FIGS. 17A and 17B each illustrate a liquid crystal display device;

FIGS. 18A and 18B illustrate a liquid crystal display device; and

FIGS. 19A to 19D illustrate a manufacturing method of a liquid crystaldisplay device.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described with reference to the accompanyingdrawings. However, the present invention is not limited to the followingdescription, and it will be easily understood by those skilled in theart that various changes and modifications can be made in modes anddetails without departing from the spirit and scope of the presentinvention. Therefore, the present invention should not be construed asbeing limited to the description of the following embodiments. Note thata common reference numeral refers to the same part or a part having asimilar function throughout the drawings in the structures describedbelow, and the description thereof is omitted.

Embodiment 1

Liquid crystal display devices and manufacturing methods thereof will bedescribed with reference to FIG. 1, FIG. 2, and FIGS. 17A and 17B.

FIG. 1, FIG. 2, and FIGS. 17A and 17B are cross-sectional views ofliquid crystal display devices.

In FIG. 1 and FIG. 2, an element layer 203 (see FIGS. 17A and 17B) isformed over a first substrate 200 which is an element substrate, aninterlayer film 209 is formed over the element layer 203, and a pixelelectrode layer 230 is provided over the interlayer film 209. A liquidcrystal layer 208 is sealed between the pixel electrode layer 230 and acounter electrode layer 231 formed on a second substrate 201 which is acounter substrate.

A mode of a liquid crystal display device illustrated in FIG. 1 includesa plurality of pixels in matrix. In each of the pixels, a thin filmtransistor including an oxide semiconductor layer, an interlayer filmover the thin film transistor, a pixel electrode layer over theinterlayer film, and a liquid crystal layer over the pixel electrodelayer are included, and the interlayer film is a light-transmittingchromatic color resin layer.

The element layer 203 (see FIGS. 17A and 17B) is provided with aplurality of pixels in matrix, and each of the pixels includes a thinfilm transistor 220 including an oxide semiconductor layer. The thinfilm transistor 220 is an inverted staggered thin film transistor, whichincludes, over the first substrate 200 which is a substrate having aninsulating surface, a gate electrode layer 221, a gate insulating layer222, a semiconductor layer 223, n⁺ layers 224 a and 224 b serving as asource region and a drain region, and wiring layers 225 a and 225 bserving as a source electrode layer and a drain electrode layer. Inaddition, the thin film transistor 220 is covered with an insulatingfilm 227.

The interlayer film 209 of the liquid crystal display device illustratedin FIG. 1 includes a light-transmitting chromatic color resin layer 204as a film having a function of attenuating the intensity of transmittingvisible light. The transmittance of visible light of thelight-transmitting chromatic color resin layer 204 is lower than that ofthe semiconductor layer 223 which is an oxide semiconductor layer.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film 209 provided over the thin filmtransistor 220, the intensity of incident light on the semiconductorlayer 223 of the thin film transistor 220 can be attenuated withoutreduction in an aperture ratio of a pixel. Accordingly, electriccharacteristics of the thin film transistor 220 can be prevented frombeing varied due to photosensitivity of the oxide semiconductor and canbe stabilized. Further, the light-transmitting chromatic color resinlayer can serve as a color filter layer. In the case of providing acolor filter layer on the counter substrate side, precise positionalalignment of a pixel region with an element substrate over which a thinfilm transistor is formed is difficult and accordingly there is apossibility that image quality is degraded. Here, since the interlayerfilm is formed as the color filter layer directly on the elementsubstrate side, the formation region can be controlled more preciselyand this structure is adjustable to a pixel with a fine pattern. Inaddition, one insulating layer can serve as both the interlayer film andthe color filter layer, whereby the process can be simplified and aliquid crystal display device can be manufactured at low cost.

Chromatic colors are colors except achromatic colors such as black,gray, and white. The coloring layer is formed using a material whichtransmits only light of a chromatic color which the material is coloredin so as to serve as a color filter. As a chromatic color, red, green,blue, or the like can be used. Alternatively, cyan, magenta, yellow, orthe like may be used. “Transmitting only light of a chromatic colorwhich a material is colored in” means that light transmitted through thecoloring layer has a peak at the wavelength of the chromatic colorlight.

The thickness of the light-transmitting chromatic color resin layer 204is preferably controlled as appropriate and optimized in considerationof the relation between the concentration of the coloring material to beincluded and the transmittance, in order that the light-transmittingchromatic color resin layer 204 functions as a coloring layer (a colorfilter). In the case where the interlayer film 209 is formed of aplurality of thin films, if at least one layer thereof is alight-transmitting chromatic color resin layer, the interlayer film 209can function as a color filter.

In the case where the thickness of the light-transmitting chromaticcolor resin layer varies depending on the chromatic colors or in thecase where there is surface unevenness due to a light-blocking layer ora thin film transistor, an insulating layer which transmits light in avisible wavelength range (a so-called colorless, transparent insulatinglayer) may be stacked for planarization of the surface of the interlayerfilm. The planarization of the interlayer film enables favorablecoverage by a pixel electrode layer or a common electrode layer to beformed thereover and uniform gap (thickness) of a liquid crystal layer,whereby the visibility of the liquid crystal display device is increasedand higher image quality can be achieved.

As the film having a function of attenuating the intensity oftransmitting visible light, a coloring layer serving as a light-blockinglayer can also be used. A liquid crystal display device illustrated inFIG. 2 is an example in which the interlayer film 209 includes thelight-transmitting chromatic color resin layer 204 and thelight-blocking layer 205 and in which the light-blocking layer 205 isused as a film having a function of attenuating the intensity oftransmitting visible light provided over the semiconductor layer 223.The transmittance of visible light of the light-blocking layer 205 islower than that of the semiconductor layer 223 which is an oxidesemiconductor layer.

The mode of the liquid crystal display device illustrated in FIG. 2includes a plurality of pixels in matrix. In each of the pixels, a thinfilm transistor including an oxide semiconductor layer, an interlayerfilm including a light-blocking layer and a light-transmitting chromaticcolor resin layer, a pixel electrode layer, and a liquid crystal layerover the pixel electrode layer are included. In the interlayer film, thelight-blocking layer is provided over the thin film transistor, and thepixel electrode layer is provided over the light-transmitting chromaticcolor resin layer.

As the light-transmitting chromatic color resin layer 204, alight-transmitting organic resin, a chromatic pigment, or a dye can beused, and an organic resin in which a pigment, a dye, or the like ismixed may be used. As the light-transmitting organic resin, aphotosensitive or non-photosensitive resin can be used.

The formation method of the light-transmitting chromatic color resinlayer 204 is not particularly limited, and a wet method such as spincoating, dip coating, spray coating, droplet discharging (e.g., inkjetting, screen printing, or offset printing), or the like may be usedin accordance with the material. If needed, an etching method (dryetching or wet etching) may be employed to form a desired pattern.

When the light-blocking layer 205 (black matrix) is used in theinterlayer film 209 provided over the thin film transistor 220, thelight-blocking layer 205 can block incident light on the semiconductorlayer 223 of the thin film transistor 220; accordingly, electriccharacteristics of the thin film transistor 220 can be prevented frombeing varied due to photosensitivity of the oxide semiconductor and canbe stabilized. Further, the light-blocking layer 205 can prevent lightleakage to an adjacent pixel, which enables higher contrast and higherdefinition display. Therefore, high definition and high reliability ofthe liquid crystal display device can be achieved.

A light-blocking layer may be further formed on the counter substrateside of the liquid crystal display device. Accordingly, contrast can beincreased and the thin film transistor can be stabilized more. In thecase of forming the light-blocking layer on the counter substrate side,if the light-blocking layer is formed in a region corresponding to thethin film transistor with the liquid crystal layer interposedtherebetween (at least in a region which overlaps with the semiconductorlayer of the thin film transistor), electric characteristics of the thinfilm transistor can be prevented from being varied due to incident lightfrom the counter substrate.

In the case of forming the light-blocking layer on the counter substrateside, there is a case in which light from the element substrate andlight from the counter substrate to the semiconductor layer of the thinfilm transistor can be blocked by a light-blocking wiring layer,electrode layer, or the like. Thus, the light-blocking layer need notalways be formed to cover the thin film transistor.

The light-blocking layer 205 is formed using a light-blocking materialthat reflects or absorbs light. For example, a black organic resin canbe used, which can be formed by mixing a black resin of a pigmentmaterial, carbon black, titanium black, or the like into a resinmaterial such as photosensitive or non-photosensitive polyimide.Alternatively, a light-blocking metal film can be used, which may beformed using chromium, molybdenum, nickel, titanium, cobalt, copper,tungsten, aluminum, or the like, for example.

The formation method of the light-blocking layer 205 is not particularlylimited, and a dry method such as vapor deposition, sputtering, CVD, orthe like or a wet method such as spin coating, dip coating, spraycoating, droplet discharging (e.g., ink jetting, screen printing, oroffset printing), or the like may be used in accordance with thematerial. If needed, an etching method (dry etching or wet etching) maybe employed to form a desired pattern.

In this specification, a thin film expressed by InMO₃(ZnO)_(m)(m>0) ispreferably used for an oxide semiconductor. A thin film ofInMO₃(ZnO)_(m)(m>0) is formed, and the thin film transistor 220 uses thethin film for the semiconductor layer 223. Note that M represents one ormore of metal elements selected from gallium (Ga), iron (Fe), nickel(Ni), manganese (Mn), aluminum (Al), and cobalt (Co). As well as thecase where only Ga is contained as M, there is a case where Ga and anyof the above metal elements except Ga, for example, Ga and Ni or Ga andFe are contained as M. Moreover, in the oxide semiconductor, in somecases, a transition metal element such as Fe or Ni or an oxide of thetransition metal is contained as an impurity element in addition to themetal element contained as M. For example, an In—Ga—Zn—O basednon-single-crystal film can be used as an oxide semiconductor layer.However, the semiconductor layer 223 is not limited to an oxidesemiconductor layer including a material whose composition formula isrepresented as InMO₃ (ZnO)_(m) (m>0) as long as it contains at least oneof indium, gallium, zinc, and tin. For example, an oxide semiconductorlayer formed using zinc oxide (ZnO), tin oxide (SnO), indium zinc oxide(IZO), indium tin oxide (ITO), indium tin oxide containing silicon oxide(ITSO), indium zinc oxide containing silicon oxide, gallium-doped zincoxide (GZO), or the like may be used.

When M is gallium (Ga) in the InMO₃(ZnO)_(m)(m>0) film (layer), thisthin film is also called an In—Ga—Zn—O based non-single-crystal film inthis specification. Even after the In—Ga—Zn—O based non-single-crystalfilm formed by a sputtering method is subjected to heat treatment at200° C. to 500° C., typically 300° C. to 400° C. for 10 minutes to 100minutes, an amorphous structure is observed in the In—Ga—Zn—O basednon-single-crystal film by X-ray diffraction (XRD). In addition, a thinfilm transistor having electric characteristics such as an on/off ratioof greater than or equal to 10⁹ and a mobility of greater than or equalto 10 at a gate voltage of ±20 V can be manufactured. The In—Ga—Zn—Obased non-single-crystal film formed by a sputtering method using atarget in which In₂O₃, Ga₂O₃, and ZnO are contained at a ratio of 1:1:1has photosensitivity to a wavelength of 450 nm or lower.

The structure of the thin film transistor formed in the liquid crystaldisplay device is not particularly limited. The thin film transistor mayhave a single-gate structure in which one channel formation region isformed, a double-gate structure in which two channel formation regionsare formed, or a triple-gate structure in which three channel formationregions are formed. In addition, the transistor in the peripheral drivercircuit region may also have a single-gate structure, a double-gatestructure, or a triple-gate structure.

The thin film transistor may have a top-gate structure (e.g., astaggered structure or a coplanar structure), a bottom-gate structure(e.g., an inverted staggered structure or an inverted coplanarstructure), a dual-gate structure including two gate electrode layersprovided over and under a channel region each with a gate insulatingfilm interposed therebetween, or other structures.

Although not illustrated in FIG. 1 and FIG. 2, an optical film such asan alignment film, a polarizing plate, a retardation plate, or ananti-reflection film may be provided as appropriate. For example,circular polarization may be employed using a polarizing plate or aretardation plate. Further, a backlight, a sidelight, or the like may beused as a light source.

The light-blocking layer may be provided so as to be stacked over orbelow the light-transmitting chromatic color resin layer. Examples ofthe stacked structure of the light-blocking layer and thelight-transmitting chromatic color resin layer are illustrated in FIGS.17A and 17B. In FIGS. 17A and 17B, the element layer 203 is formed overthe first substrate 200 which is an element substrate and the interlayerfilm 209 is formed over the element layer 203. The interlayer film 209includes light-transmitting chromatic color resin layers 204 a, 204 b,and 204 c and light-blocking layers 205 a, 205 b, 205 c, and 205 d. Thelight-blocking layers 205 a, 205 b, 205 c, and 205 d are formed atboundaries of the light-transmitting chromatic color resin layers 204 a,204 b, and 204 c. Note that the pixel electrode layer and the commonelectrode layer are omitted in FIGS. 17A and 17B.

A plurality of chromatic colors can be used, and for example, the liquidcrystal display device in FIGS. 17A and 17B uses a coloring layer ofred, a coloring layer of green, and a coloring layer of blue as thelight-transmitting chromatic color resin layer 204 a, thelight-transmitting chromatic color resin layer 204 b, and thelight-transmitting chromatic color resin layer 204 c, respectively;thus, light-transmitting chromatic color resin layers of plural colorsare used.

FIGS. 17A and 17B illustrate examples in which thin films that arethinner than the light-transmitting chromatic color resin layers areused as the light-blocking layers and the light-blocking layers arestacked below or over the light-transmitting chromatic color resinlayers. As such light-blocking layers, thin films of light-blockinginorganic films (e.g., metal films) are preferable.

In FIG. 17A, thin films of the light-blocking layers 205 a, 205 b, 205c, and 205 d are formed over the element layer 203, and thelight-transmitting chromatic color resin layers 204 a, 204 b, and 204 care stacked over the light-blocking layers 205 a, 205 b, 205 c, and 205d. In FIG. 17B, the light-transmitting chromatic color resin layers 204a, 204 b, and 204 c are formed over the element layer 203; thin films ofthe light-blocking layers 205 a, 205 b, 205 c, and 205 d are stackedover the light-transmitting chromatic color resin layers 204 a, 204 b,and 204 c; and an insulating film 211 is formed as an overcoat film overthe light-blocking layers 205 a, 205 b, 205 c, and 205 d. The elementlayer, the light-blocking layers, and the light-transmitting chromaticcolor resin layers may be stacked directly as illustrated in FIG. 17B,or they may have an insulating film over, below, or between the layers.

A liquid crystal material of the liquid crystal layer 208 can beappropriately selected from various liquid crystals such as a lyotropicliquid crystal, a thermotropic liquid crystal, a low molecular liquidcrystal, a high molecular liquid crystal, a discotic liquid crystal, aferroelectric liquid crystal, an anti-ferroelectric liquid crystal, andthe like.

As sealants 202 a and 202 b, it is typically preferable to use a visiblelight curable resin, an ultraviolet curable resin, or a thermosettingresin. Typically, an acrylic resin, an epoxy resin, an amine resin, orthe like can be used. Further, a photopolymerization initiator(typically, an ultraviolet light polymerization initiator), athermosetting agent, a filler, or a coupling agent may also be includedin the sealants 202 a and 202 b.

In this specification, in the case where the liquid crystal displaydevice is a transmissive liquid crystal display device (or atransflective liquid crystal display device) which performs display bytransmitting light from a light source, it is necessary that light betransmitted at least through a pixel region. Therefore, the firstsubstrate, the second substrate, and thin films included in the elementlayer such as a pixel electrode layer, a common electrode layer, otherinsulating films, and a conductive film, which exist in the pixel regionwhere light is transmitted, all have a light-transmitting property withrespect to light in a visible wavelength range.

As the first substrate 200 and the second substrate 201, a glasssubstrate of barium borosilicate glass, aluminoborosilicate glass, orthe like, a quartz substrate, a plastic substrate, or the like can beused. In a liquid crystal display device which includes a thin filmtransistor formed by using an oxide semiconductor layer for a channel,an interlayer film which covers at least the oxide semiconductor layeris formed using a material which attenuates the intensity oftransmitting visible light. Accordingly, operation characteristics ofthe thin film transistor can be stabilized without reduction in anaperture ratio. Therefore, the liquid crystal display device includingthe thin film transistor can have high reliability.

Embodiment 2

A liquid crystal display device will be described with reference toFIGS. 18A and 18B.

FIG. 18A is a plan view of a liquid crystal display device illustratingone pixel. FIG. 18B is a cross-sectional view taken along line X1-X2 inFIG. 18A.

In FIG. 18A, a plurality of source wiring layers (including a wiringlayer 405 a) are provided in parallel to each other (extended in avertical direction in the drawing) and apart from each other. Aplurality of gate wiring layers (including a gate electrode layer 401)are provided apart from each other and extend in a direction generallyperpendicular to the source wiring layers (a horizontal direction in thedrawing). Common wiring layers 408 are provided adjacent to theplurality of gate wiring layers and extend in a direction generallyparallel to the gate wiring layers, that is, in a direction generallyperpendicular to the source wiring layers (a horizontal direction in thedrawing). Roughly rectangular spaces are surrounded by the source wiringlayers, the common wiring layers 408, and the gate wiring layers, and apixel electrode layer and a common wiring layer of a liquid crystaldisplay device are provided in these spaces. A thin film transistor 420for driving the pixel electrode layer is provided at the upper leftcorner in the drawing. A plurality of pixel electrode layers and thinfilm transistors are provided in matrix.

In the liquid crystal display device of FIGS. 18A and 18B, a firstelectrode layer 447 electrically connected to the thin film transistor420 serves as a pixel electrode layer and a second electrode layer 446electrically connected to the common wiring layer 408 serves as a commonelectrode layer. Note that a capacitor is formed by the first electrodelayer and the common wiring layer. Although a common electrode layer canoperate in a floating state (an electrically isolated state), thepotential of the common electrode layer may be set to a fixed potential,preferably to a potential around a common potential (an intermediatepotential of an image signal which is transmitted as data) in such alevel as not to generate flickers.

A method in which the gray scale is controlled by generating an electricfield generally parallel (i.e., in a lateral direction) to a substrateto move liquid crystal molecules in a plane parallel to the substratecan be used. For such a method, an electrode structure used in IPS modeas illustrated in FIGS. 18A and 18B can be employed.

In a lateral electric field mode such as IPS mode, a first electrodelayer (e.g., a pixel electrode layer with which voltage is controlledper pixel) and a second electrode layer (e.g., a common electrode layerwith which common voltage is applied to all pixels), which have anopening pattern, are located below a liquid crystal layer. Therefore,the first electrode layer 447 and the second electrode layer 446, one ofwhich is a pixel electrode layer and the other of which is a commonelectrode layer, are formed over a first substrate 441, and at least oneof the first electrode layer and the second electrode layer is formedover an interlayer film. The first electrode layer 447 and the secondelectrode layer 446 have not a plane shape but various opening patternsincluding a bent portion or a comb-shaped portion. The first electrodelayer 447 and the second electrode layer 446 are arranged so that theydo not have the same shape and do not overlap with each other, in orderto generate electric field therebetween.

By application of electric field between the pixel electrode layer andthe common electrode layer, a liquid crystal is controlled. An electricfield in a lateral direction is applied to the liquid crystal, so thatliquid crystal molecules can be controlled using the electric field.That is, the liquid crystal molecules oriented parallel to the substratecan be controlled in a direction parallel to the substrate; accordingly,the viewing angle can be widened.

Other examples of the first electrode layer 447 and the second electrodelayer 446 are illustrated in FIGS. 8A to 8D. As illustrated in the topviews of FIGS. 8A to 8D, first electrode layers 447 a to 447 d andsecond electrode layers 446 a to 446 d are arranged alternately. In FIG.8A, the first electrode layer 447 a and the second electrode layer 446 ahave a wavelike shape with curves. In FIG. 8B, the first electrode layer447 b and the second electrode layer 446 b have a shape with concentriccircular openings. In FIG. 8C, the first electrode layer 447 c and thesecond electrode layer 446 c have a comb-shape and partially overlapwith each other. In FIG. 8D, the first electrode layer 447 d and thesecond electrode layer 446 d have a comb-shape in which the electrodelayers are engaged with each other. In the case where the firstelectrode layer 447 a, 447 b, or 447 c overlaps with the secondelectrode layer 446 a, 446 b, or 446 c as illustrated in FIGS. 8A to 8C,an insulating film is formed between the first electrode layer 447 andthe second electrode layer 446 so that the first electrode layer 447 andthe second electrode layer 446 are formed over different films.

The thin film transistor 420 is an inverted staggered thin filmtransistor and includes, over the first substrate 441 having aninsulating surface, the gate electrode layer 401, a gate insulatinglayer 402, a semiconductor layer 403, n⁺ layers 404 a and 404 b servingas a source region and a drain region, and wiring layers 405 a and 405 bserving as a source electrode layer and a drain electrode layer.

An insulating film 407 is provided in contact with the semiconductorlayer 403 so as to cover the thin film transistor 420. An interlayerfilm 413 is provided over the insulating film 407, and the firstelectrode layer 447 and the second electrode layer 446 are formed overthe interlayer film 413.

In the interlayer film 413 of the liquid crystal display device of FIGS.18A and 18B, a light-transmitting chromatic color resin layer 417 isused as a film having a function of attenuating the intensity oftransmitting visible light.

When a coloring layer of the light-transmitting chromatic color resinlayer 417 is used as the interlayer film 413 provided over the thin filmtransistor 420, the intensity of incident light on the semiconductorlayer 403 of the thin film transistor 420 can be attenuated withoutreduction in an aperture ratio of a pixel. Accordingly, electriccharacteristics of the thin film transistor 420 can be prevented frombeing varied due to photosensitivity of the oxide semiconductor and canbe stabilized. Further, the light-transmitting chromatic color resinlayer 417 can serve as a color filter layer. In the case of providing acolor filter layer on the counter substrate side, precise positionalalignment of a pixel region with an element substrate over which a thinfilm transistor is formed is difficult and accordingly there is apossibility that image quality is degraded. Here, since the interlayerfilm is formed as the color filter layer directly on the elementsubstrate side, the formation region can be controlled more preciselyand this structure is adjustable to a pixel with a fine pattern. Inaddition, one insulating layer can serve as both the interlayer film andthe color filter layer, whereby the process can be simplified and aliquid crystal display device can be manufactured at low cost.

As the light-transmitting chromatic color resin layer, a photosensitiveor non-photosensitive organic resin can be used. It is preferable to usea photosensitive organic resin layer because the number of resist maskscan be reduced and thus the process can be simplified. In addition, acontact hole formed in the interlayer film can have an opening shapewith curvature; accordingly, coverage by a film such as an electrodelayer formed in the contact hole can be improved.

The formation method of the interlayer film 413 (the light-transmittingchromatic color resin layer 417) is not particularly limited, and thefollowing method can be employed in accordance with the material: spincoating, dip coating, spray coating, droplet discharging (e.g., inkjetting, screen printing, or offset printing), doctor knife, rollcoating, curtain coating, knife coating, or the like.

A liquid crystal layer 444 is provided over the first electrode layer447 and the second electrode layer 446 and sealed with a secondsubstrate 442 which is a counter substrate.

The first substrate 441 and the second substrate 442 arelight-transmitting substrates and are provided with a polarizing plate443 a and a polarizing plate 443 b respectively on their outer sides(the sides opposite from the liquid crystal layer 444).

The first electrode layer 447 and the second electrode layer 446 can beformed using a light-transmitting conductive material such as indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, indium tin oxide (hereinafter referred to asITO), indium zinc oxide, or indium tin oxide to which silicon oxide isadded.

A conductive composition containing a conductive high molecule (alsoreferred to as a conductive polymer) can be used to form the firstelectrode layer 447 and the second electrode layer 446. The pixelelectrode formed using the conductive composition preferably has a sheetresistance of 10000 ohms per square or less and a transmittance of 70%or more at a wavelength of 550 nm. Furthermore, the resistivity of theconductive high molecule contained in the conductive composition ispreferably 0.1 Ω·cm or less.

As the conductive high molecule, a so-called 7 c-electron conjugatedconductive polymer can be used. For example, it is possible to usepolyaniline or a derivative thereof, polypyrrole or a derivativethereof, polythiophene or a derivative thereof, or a copolymer of two ormore kinds of them.

An insulating film serving as a base film may be provided between thefirst substrate 441 and the gate electrode layer 401. The base filmfunctions to prevent diffusion of an impurity element from the firstsubstrate 441 and can be formed using one film or stacked films selectedfrom a silicon nitride film, a silicon oxide film, a silicon nitrideoxide film, and a silicon oxynitride film. The gate electrode layer 401can be formed to have a single-layer structure or a stacked structureusing a metal material such as molybdenum, titanium, chromium, tantalum,tungsten, aluminum, copper, neodymium, or scandium or an alloy materialwhich contains any of these materials as its main component. By using alight-blocking conductive film as the gate electrode layer 401, lightfrom a backlight (light emitted through the first substrate 441) can beprevented from entering the semiconductor layer 403.

For example, as a two-layer structure of the gate electrode layer 401,the following structures are preferable: a two-layer structure of analuminum layer and a molybdenum layer stacked thereover, a two-layerstructure of a copper layer and a molybdenum layer stacked thereover, atwo-layer structure of a copper layer and a titanium nitride layer or atantalum nitride layer stacked thereover, and a two-layer structure of atitanium nitride layer and a molybdenum layer. As a three-layerstructure, a stack of a tungsten layer or a tungsten nitride layer, alayer of an alloy of aluminum and silicon or an alloy of aluminum andtitanium, and a titanium nitride layer or a titanium layer ispreferable.

The gate insulating layer 402 can be formed to have a single-layerstructure or a stacked structure using a silicon oxide layer, a siliconnitride layer, a silicon oxynitride layer, or a silicon nitride oxidelayer by a plasma CVD method, a sputtering method, or the like.Alternatively, the gate insulating layer 402 can be formed using asilicon oxide layer by a CVD method using an organosilane gas. As theorganosilane gas, a silicon-containing compound such astetraethoxysilane (TEOS: chemical formula, Si(OC₂H₅)₄),tetramethylsilane (TMS: chemical formula, Si(CH₃)₄),tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane(OMCTS), hexamethyldisilazane (HMDS), triethoxysilane (SiH(OC₂H₅)₃), ortrisdimethylaminosilane (SiH(N(CH₃)₂)₃) can be used.

It is preferable that reverse sputtering in which an argon gas isintroduced to generate plasma be performed before the formation of theoxide semiconductor film used as the semiconductor layer 403 in order toremove dust attached to a surface of the gate insulating layer. Notethat instead of an argon atmosphere, a nitrogen atmosphere, a heliumatmosphere, or the like may be used. Alternatively, an argon atmosphereto which oxygen, hydrogen, N₂O, or the like is added may be used.Further alternatively, an argon atmosphere to which Cl₂, CF₄, or thelike is added may be used.

The semiconductor layer 403 and the n⁺ layers 404 a and 404 b serving asa source region and a drain region can be formed using an In—Ga—Zn—Obased non-single-crystal film. The n⁺ layers 404 a and 404 b are oxidesemiconductor layers having a resistance lower than the semiconductorlayer 403. For example, the n⁺ layers 404 a and 404 b have n-typeconductivity and an activation energy (ΔE) of 0.01 to 0.1 eV inclusive.The n⁺ layers 404 a and 404 b are In—Ga—Zn—O based non-single-crystalfilms and include at least an amorphous component. The n⁺ layers 404 aand 404 b may include crystal grains (nanocrystals) in an amorphousstructure. These crystal grains (nanocrystals) in the n⁺ layers 404 aand 404 b each have a diameter of 1 nm to 10 nm, typically about 2 nm to4 nm.

By the provision of the n⁺ layers 404 a and 404 b, the wiring layers 405a and 405 b which are metal layers can have a good junction with thesemiconductor layer 403 which is an oxide semiconductor layer, so thatstable operation can be realized in terms of heat in comparison with aSchottky junction. In addition, willing provision of the n⁺ layer iseffective in supplying carriers to the channel (on the source side),stably absorbing carriers from the channel (on the drain side), orpreventing a resistance component from being formed at an interfacebetween the wiring layer and the semiconductor layer. Moreover, sinceresistance is reduced, good mobility can be ensured even with a highdrain voltage.

The first In—Ga—Zn—O based non-single-crystal film used as thesemiconductor layer 403 is formed under deposition conditions differentfrom those for the second In—Ga—Zn—O based non-single-crystal film whichis used as the n⁺ layers 404 a and 404 b. For example, the firstIn—Ga—Zn—O based non-single-crystal film is formed under conditionswhere the ratio of an oxygen gas flow rate to argon gas flow rate ishigher than the ratio of an oxygen gas flow rate to an argon gas flowrate under the deposition conditions for the second In—Ga—Zn—O basednon-single-crystal film. Specifically, the second In—Ga—Zn—O basednon-single-crystal film is formed in a rare gas (e.g., argon or helium)atmosphere (or an atmosphere, less than or equal to 10% of which is anoxygen gas and greater than or equal to 90% of which is an argon gas),and the first In—Ga—Zn—O based non-single-crystal film is formed in anoxygen atmosphere (or an atmosphere in which the oxygen gas flow rate ishigher than or equal to the argon gas flow rate).

For example, the first In—Ga—Zn—O based non-single-crystal film used asthe semiconductor layer 403 is formed in an argon or oxygen atmosphereusing an oxide semiconductor target having a diameter of 8 inches andincluding In, Ga, and Zn (In₂O₃: Ga₂O₃: ZnO=1:1:1), with the distancebetween the substrate and the target set to 170 mm, under a pressure of0.4 Pa, and with a direct-current (DC) power source of 0.5 kW. Note thatit is preferable to use a pulsed direct-current (DC) power source, withwhich dust can be reduced and thickness distribution can be evened. Thefirst In—Ga—Zn—O based non-single-crystal film has a thickness of 5 nmto 200 nm.

On the contrary, the second oxide semiconductor film used as the n⁺layers 404 a and 404 b is formed by a sputtering method, which isperformed using a target (In₂O₃: Ga₂O₃: ZnO=1:1:1) under depositionconditions where the pressure is 0.4 Pa, the power is 500 W, thedeposition temperature is room temperature, and an argon gas isintroduced at a flow rate of 40 sccm. An In—Ga—Zn—O basednon-single-crystal film including crystal grains with a size of 1 nm to10 nm immediately after the film formation is formed in some cases. Notethat it can be said that the presence or absence of crystal grains orthe density of crystal grains can be adjusted and the diameter size canbe adjusted within the range of 1 nm to 10 nm by appropriate adjustmentof the reactive sputtering deposition conditions such as the compositionratio in the target, the film deposition pressure (0.1 Pa to 2.0 Pa),the power (250 W to 3000 W: 8 inches 0), the temperature (roomtemperature to 100° C.), and the like. The second In—Ga—Zn—O basednon-single-crystal film has a thickness of 5 nm to 20 nm. Needless tosay, when the film includes crystal grains, the size of the crystalgrains does not exceed the thickness of the film. The second In—Ga—Zn—Obased non-single-crystal film has a thickness of 5 nm.

Examples of a sputtering method include an RF sputtering method in whicha high-frequency power source is used as a sputtering power source, a DCsputtering method, and a pulsed DC sputtering method in which a bias isapplied in a pulsed manner. An RF sputtering method is mainly used inthe case where an insulating film is formed, and a DC sputtering methodis mainly used in the case where a metal film is formed.

In addition, there is also a multi-source sputtering apparatus in whicha plurality of targets of different materials can be set. With themulti-source sputtering apparatus, films of different materials can beformed to be stacked in the same chamber, or a film of plural kinds ofmaterials can be formed by electric discharge at the same time in thesame chamber.

In addition, there are a sputtering apparatus provided with a magnetsystem inside the chamber and used for a magnetron sputtering, and asputtering apparatus used for an ECR sputtering in which plasmagenerated with the use of microwaves is used without using glowdischarge.

Furthermore, as a deposition method by sputtering, there are also areactive sputtering method in which a target substance and a sputteringgas component are chemically reacted with each other during depositionto form a thin compound film thereof, and a bias sputtering method inwhich a voltage is also applied to a substrate during deposition.

In the manufacturing process of the semiconductor layer, the n⁺ layers,and the wiring layers, an etching step is used to process thin filmsinto desired shapes. Dry etching or wet etching can be used for theetching step.

As an etching gas used for dry etching, a gas containing chlorine (achlorine-based gas such as chlorine (Cl₂), boron chloride (BCl₃),silicon chloride (SiCl₄), or carbon tetrachloride (CCl₄)) is preferable.

Alternatively, a gas containing fluorine (a fluorine-based gas such ascarbon tetrafluoride (CF₄), sulfur fluoride (SF₆), nitrogen fluoride(NF₃), or trifluoromethane (CHF₃)), hydrogen bromide (HBr), oxygen (O₂),any of these gases to which a rare gas such as helium (He) or argon (Ar)is added, or the like can be used.

As an etching apparatus used for dry etching, an etching apparatus thatuses reactive ion etching (RIE), or a dry etching apparatus that uses ahigh-density plasma source such as an electron cyclotron resonance (ECR)source or an inductively coupled plasma (ICP) source can be used. Assuch a dry etching apparatus with which uniform discharge can be easilyobtained over a large area as compared to an ICP etching apparatus,there is an enhanced capacitively coupled plasma (ECCP) mode etchingapparatus in which an upper electrode is grounded, a high-frequencypower source of 13.56 MHz is connected to a lower electrode, and furthera low-frequency power source of 3.2 MHz is connected to the lowerelectrode. This ECCP mode etching apparatus, if used, can be appliedeven when a substrate having the size exceeding 3 meters of the tenthgeneration is used as the substrate, for example.

In order to perform etching to desired shapes, etching conditions (e.g.,the amount of electric power applied to a coiled electrode, the amountof electric power applied to an electrode on a substrate side, or theelectrode temperature on the substrate side) are controlled asappropriate.

As an etchant used for wet etching, a mixed solution of phosphoric acid,acetic acid, and nitric acid, an ammonia peroxide mixture (hydrogenperoxide:ammonia:water=5:2:2), or the like can be used. Alternatively,ITO-07N (produced by Kanto Chemical Co., Inc.) may be used.

The etchant after the wet etching is removed by cleaning, together withthe etched material. The waste liquid of the etchant including theetched material may be purified so that the included material is reused.If a material such as indium included in the oxide semiconductor layeris collected from the waste liquid of the etching and reused, resourcescan be used effectively and cost can be reduced.

In order to perform etching to desired shapes, etching conditions (e.g.,etchant, etching time, temperature, or the like) are controlled asappropriate in accordance with the material.

As a material of the wiring layers 405 a and 405 b, an element selectedfrom Al, Cr, Ta, Ti, Mo, and W, an alloy containing any of the elementsas its component, an alloy containing any of the elements incombination, and the like can be given. Further, in the case ofperforming heat treatment at 200° C. to 600° C., the conductive filmpreferably has heat resistance against such heat treatment. Since use ofAl alone brings disadvantages such as low resistance and a tendency tocorrosion, aluminum is used in combination with a conductive materialhaving heat resistance. As the conductive material having heatresistance which is used in combination with Al, any of the followingmaterials may be used: an element selected from titanium (Ti), tantalum(Ta), tungsten (W), molybdenum (Mo), chromium (Cr), neodymium (Nd), andscandium (Sc), an alloy containing any of the above elements as acomponent, an alloy containing any of the above elements in combination,and a nitride containing any of the above elements as a component.

The gate insulating layer 402, the semiconductor layer 403, the n⁺layers 404 a and 404 b, and the wiring layers 405 a and 405 b may beformed in succession without being exposed to air. By successiveformation without exposure to air, each interface between the stackedlayers can be formed without being contaminated by atmosphericcomponents or contaminating impurities contained in air; therefore,variation in characteristics of the thin film transistor can be reduced.

Note that the semiconductor layer 403 is partially etched and has agroove (a depression portion).

The semiconductor layer 403 and the n⁺ layers 404 a and 404 b arepreferably subjected to heat treatment at 200° C. to 600° C., typically300° C. to 500° C. For example, heat treatment is performed for 1 hourat 350° C. in a nitrogen atmosphere. By this heat treatment,rearrangement at the atomic level is caused in the In—Ga—Zn—O basedoxide semiconductor which forms the semiconductor layer 403 and the n⁺layers 404 a and 404 b. This heat treatment (also includingphoto-annealing or the like) is important in that the distortion thatinterrupts carrier transfer in the semiconductor layer 403 and the n⁺layers 404 a and 404 b can be reduced. Note that there is no particularlimitation on when to perform the heat treatment, as long as it isperformed after the semiconductor layer 403 and the n⁺ layers 404 a and404 b are formed.

In addition, oxygen radical treatment may be performed on the exposeddepression portion of the semiconductor layer 403. The radical treatmentis preferably performed in an atmosphere of O₂ or N₂O, or an atmosphereof N₂, He, Ar, or the like which includes oxygen. Alternatively, anatmosphere obtained by adding Cl₂ or CF₄ to the above atmosphere may beused. Note that the radical treatment is preferably performed with nobias voltage applied to the first substrate 441 side.

The insulating film 407 covering the thin film transistor 420 can beformed using an inorganic insulating film or organic insulating filmformed by a wet method or a dry method. For example, the insulating film407 can be formed by a CVD method, a sputtering method, or the likeusing a silicon nitride film, a silicon oxide film, a silicon oxynitridefilm, an aluminum oxide film, a tantalum oxide film, or the like.Alternatively, an organic material such as acrylic, polyimide,benzocyclobutene, polyamide, or an epoxy resin can be used. Other thansuch organic materials, it is also possible to use a low-dielectricconstant material (a low-k material), a siloxane-based resin, PSG(phosphosilicate glass), BPSG (borophosphosilicate glass), or the like.

Note that a siloxane-based resin is a resin formed using asiloxane-based material as a starting material and having the bond ofSi—O—Si. A siloxane-based resin may include, as a substituent, anorganic group (e.g., an alkyl group or an aryl group) or a fluoro group.The organic group may include a fluoro group. A siloxane-based resin isapplied by a coating method and baked; thus, the insulating film 407 canbe formed.

Alternatively, the insulating film 407 may be formed by stacking pluralinsulating films formed using any of these materials. For example, theinsulating film 407 may have such a structure that an organic resin filmis stacked over an inorganic insulating film.

Further, by using a resist mask which is formed using a multi-tone maskand has regions with plural thicknesses (typically, two differentthicknesses), the number of resist masks can be reduced, resulting insimplified process and lower cost.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

Embodiment 3

In Embodiment 3, examples in which a pixel electrode layer and a commonelectrode layer are formed in different planes will be described withreference to FIGS. 3A and 3B, FIGS. 4A and 4B, and FIGS. 7A and 7B. Notethat components in common with those in Embodiments 1 and 2 can beformed using a similar material and manufacturing method, and detaileddescription of the same portions and portions having similar functionsis omitted.

FIG. 3A, FIG. 4A, and FIG. 7A are plan views of liquid crystal displaydevices, each illustrating one pixel. FIG. 3B, FIG. 4B, and FIG. 7B arecross-sectional views taken along line X1-X2 in FIG. 3A, FIG. 4A, andFIG. 7A, respectively.

In each of the plan views of FIG. 3A, FIG. 4A, and FIG. 7A, in a mannersimilar to that of Embodiment 2, a plurality of source wiring layers(including a wiring layer 405 a) are provided in parallel to each other(extended in a vertical direction in the drawing) and apart from eachother. A plurality of gate wiring layers (including a gate electrodelayer 401) are provided apart from each other and extend in a directiongenerally perpendicular to the source wiring layers (a horizontaldirection in the drawing). Common wiring layers 408 are providedadjacent to the plurality of gate wiring layers and extend in adirection generally parallel to the gate wiring layers, that is, in adirection generally perpendicular to the source wiring layers (ahorizontal direction in the drawing). Roughly rectangular spaces aresurrounded by the source wiring layers, the common wiring layers 408,and the gate wiring layers, and a pixel electrode layer and a commonwiring layer of a liquid crystal display device are provided in thesespaces. A thin film transistor 420 for driving the pixel electrode layeris provided at the upper left corner in the drawing. A plurality ofpixel electrode layers and thin film transistors are provided in matrix.

The liquid crystal display devices of FIGS. 3A and 3B, FIGS. 4A and 4B,and FIGS. 7A and 7B are each provided with a first electrode layer 447which is a pixel electrode layer and a second electrode layer 446 whichis a common electrode layer over different films (over different layers)as illustrated in the cross-sectional views of FIG. 3B, FIG. 4B, andFIG. 7B. FIG. 3B, FIG. 4B, and FIG. 7B each illustrate an example inwhich the first electrode layer 447 which is a pixel electrode layer isformed below the second electrode layer 446 which is a common electrodelayer with an insulating film interposed therebetween. However, thesecond electrode layer 446 which is a common electrode layer may beformed below the first electrode layer 447 which is a pixel electrodelayer with an insulating film interposed therebetween.

In each of the liquid crystal display devices of FIG. 3A, FIG. 4A, andFIG. 7A, the first electrode layer 447 which is electrically connectedto the thin film transistor 420 serves as a pixel electrode layer, whilethe second electrode layer 446 which is electrically connected to thecommon electrode layer 408 serves as a common electrode layer.

In FIGS. 3A and 3B, the first electrode layer 447 is formed over a firstsubstrate 441; a gate insulating layer 402, a wiring layer 405 b, aninsulating film 407, and an interlayer film 413 are stacked over thefirst electrode layer 447; and the second electrode layer 446 is formedover the interlayer film 413. In FIGS. 3A and 3B, a capacitor is formedby the first electrode layer 447 and a wiring layer 410 formed in thesame step as that of the wiring layers 405 a and 405 b.

In FIGS. 4A and 4B, the first electrode layer 447 is formed over aninsulating film 407; an interlayer film 413 is stacked over the firstelectrode layer 447; and the second electrode layer 446 is formed overthe interlayer film 413. In FIGS. 4A and 4B, a capacitor is formed bythe first electrode layer and the common wiring layer.

In FIGS. 7A and 7B, the first electrode layer 447 is formed over aninterlayer film 413; an insulating film 416 is stacked over the firstelectrode layer 447; and the second electrode layer 446 is formed overthe insulating film 416. In FIGS. 7A and 7B, a capacitor is formed bythe first electrode layer and the common wiring layer. FIGS. 7A and 7Billustrate an example where the first electrode layer 447 and the secondelectrode layer 446 have a comb-shape in which the angle of a bentportion is 90 degrees. When the angle of the bent portion in the firstelectrode layer 447 and the second electrode layer 446 is 90 degrees,the angle difference between the polarizing axis of a polarizing plateand the orientation angle of liquid crystal molecules is 45 degrees, andat this time, transmittance in white display can be maximized.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film provided over the thin filmtransistor, the intensity of incident light on a semiconductor layer ofthe thin film transistor can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistor can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

Embodiment 4

A liquid crystal display device including a light-blocking layer (ablack matrix) will be described with reference to FIGS. 5A and 5B.

The liquid crystal display device illustrated in FIGS. 5A and 5B is anexample in which a light-blocking layer 414 is further formed on thesecond substrate (the counter substrate) 442 side in the liquid crystaldisplay device illustrated in FIGS. 18A and 18B of Embodiment 2.Therefore, components in common with those in Embodiment 2 can be formedusing a similar material and manufacturing method, and detaileddescription of the same portions and portions having similar functionsis omitted.

FIG. 5A is a plan view of the liquid crystal display device, and FIG. 5Bis a cross-sectional view taken along line X1-X2 in FIG. 5A. Note thatthe plan view of FIG. 5A illustrates only the element substrate side andthe counter substrate side is not illustrated.

The light-blocking layer 414 is formed on the liquid crystal layer 444side of the second substrate 442 and an insulating layer 415 is formedas a planarization film. The light-blocking layer 414 is preferablyformed in a region corresponding to the thin film transistor 420 withthe liquid crystal layer 444 (a region which overlaps with asemiconductor layer of the thin film transistor) interposedtherebetween. The first substrate 441 and the second substrate 442 arefirmly attached to each other with the liquid crystal layer 444interposed therebetween so that the light-blocking layer 414 ispositioned to cover at least the semiconductor layer 403 of the thinfilm transistor 420.

The light-blocking layer 414 is formed using a light-blocking materialthat reflects or absorbs light. For example, a black organic resin canbe used, which can be formed by mixing a black resin of a pigmentmaterial, carbon black, titanium black, or the like into a resinmaterial such as photosensitive or non-photosensitive polyimide.Alternatively, a light-blocking metal film can be used, which may beformed using chromium, molybdenum, nickel, titanium, cobalt, copper,tungsten, aluminum, or the like, for example.

The formation method of the light-blocking layer 414 is not particularlylimited, and a dry method such as vapor deposition, sputtering, CVD, orthe like or a wet method such as spin coating, dip coating, spraycoating, droplet discharging (e.g., ink jetting, screen printing, oroffset printing), or the like may be used in accordance with thematerial. If needed, an etching method (dry etching or wet etching) maybe employed to form a desired pattern.

The insulating layer 415 may be formed using an organic resin or thelike such as acrylic or polyimide by a coating method such as spincoating or various printing methods.

When the light-blocking layer 414 is further provided on the countersubstrate side in this manner, contrast can be increased and the thinfilm transistor can be stabilized more. The light-blocking layer 414 canblock incident light on the semiconductor layer 403 of the thin filmtransistor 420; accordingly, electric characteristics of the thin filmtransistor 420 can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized more.Further, the light-blocking layer 414 can prevent light leakage to anadjacent pixel, which enables higher contrast and higher definitiondisplay. Therefore, high definition and high reliability of the liquidcrystal display device can be achieved.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 5

A liquid crystal display device including a light-blocking layer (ablack matrix) will be described with reference to FIGS. 6A and 6B.

The liquid crystal display device illustrated in FIGS. 6A and 6B is anexample in which a light-blocking layer 414 is formed as part of theinterlayer film 413 on the first substrate 441 (the element substrate)side in the liquid crystal display device illustrated in FIGS. 18A and18B of Embodiment 2. Therefore, components in common with those inEmbodiment 2 can be formed using a similar material and manufacturingmethod, and detailed description of the same portions and portionshaving similar functions is omitted.

FIG. 6A is a plan view of a liquid crystal display device, and FIG. 6Bis a cross-sectional view taken along line X1-X2 in FIG. 6A. Note thatthe plan view of FIG. 6A illustrates only the element substrate side andthe counter substrate side is not illustrated.

The interlayer film 413 includes the light-blocking layer 414 and alight-transmitting chromatic color resin layer 417. The light-blockinglayer 414 is provided on the first substrate 441 (element substrate)side and formed over the thin film transistor 420 (at least in a regionwhich covers the semiconductor layer of the thin film transistor) withthe insulating film 407 interposed therebetween, so that thelight-blocking layer 414 serves as a light-blocking layer for thesemiconductor layer. On the contrary, the light-transmitting chromaticcolor resin layer 417 is formed so as to overlap with the firstelectrode layer 447 and the second electrode layer 446 and serves as acolor filter layer. In the liquid crystal display device of FIG. 6B,part of the second electrode layer 446 is formed over the light-blockinglayer 414 and the liquid crystal layer 444 is provided over the part ofthe second electrode layer 446.

Since the light-blocking layer 414 is used in the interlayer film, it ispreferable that black organic resin be used for the light-blocking layer414. For example, a black resin of a pigment material, carbon black,titanium black, or the like may be mixed into a resin material such asphotosensitive or non-photosensitive polyimide. As the formation methodof the light-blocking layer 414, a wet method such as spin coating, dipcoating, spray coating, droplet discharging (e.g., ink jetting, screenprinting, or offset printing), or the like may be used in accordancewith the material. If needed, an etching method (dry etching or wetetching) may be employed to form a desired pattern.

When the light-blocking layer 414 is provided in this manner, thelight-blocking layer 414 can block incident light on the semiconductorlayer 403 of the thin film transistor 420 without reduction in anaperture ratio of a pixel; accordingly, electric characteristics of thethin film transistor 420 can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-blocking layer 414 can prevent light leakage to anadjacent pixel, which enables higher contrast and higher definitiondisplay. Therefore, high definition and high reliability of the liquidcrystal display device can be achieved.

Further, the light-transmitting chromatic color resin layer 417 canserve as a color filter layer. In the case of providing a color filterlayer on the counter substrate side, precise positional alignment of apixel region with an element substrate over which a thin film transistoris formed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the light-transmitting chromatic colorresin layer 417 included in the interlayer film is formed as the colorfilter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 6

Another example of a thin film transistor that can be applied to theliquid crystal display devices in Embodiments 1 to 5 will be described.Note that components in common with those in Embodiments 2 to 5 can beformed using a similar material and manufacturing method, and detaileddescription of the same portions and portions having similar functionsis omitted.

An example of a liquid crystal display device including a thin filmtransistor which has a structure in which a source electrode layer and adrain electrode layer are in contact with a semiconductor layer withoutan n⁺ layer interposed therebetween is illustrated in FIGS. 10A and 10B.

FIG. 10A is a plan view of a liquid crystal display device illustratingone pixel. FIG. 10B is a cross-sectional view taken along line V1-V2 inFIG. 10A.

In the plan view of FIG. 10A, in a manner similar to that of Embodiment2, a plurality of source wiring layers (including a wiring layer 405 a)are provided in parallel to each other (extended in a vertical directionin the drawing) and apart from each other. A plurality of gate wiringlayers (including a gate electrode layer 401) are provided apart fromeach other and extend in a direction generally perpendicular to thesource wiring layers (a horizontal direction in the drawing). Commonwiring layers 408 are provided adjacent to the plurality of gate wiringlayers and extend in a direction generally parallel to the gate wiringlayers, that is, in a direction generally perpendicular to the sourcewiring layers (a horizontal direction in the drawing). Roughlyrectangular spaces are surrounded by the source wiring layers, thecommon wiring layers 408, and the gate wiring layers, and a pixelelectrode layer and a common wiring layer of a liquid crystal displaydevice are provided in these spaces. A thin film transistor 422 fordriving the pixel electrode layer is provided at the upper left cornerin the drawing. A plurality of pixel electrode layers and thin filmtransistors are provided in matrix.

The first substrate 441 provided with the thin film transistor 422, theinterlayer film 413 which is a light-transmitting chromatic color resinlayer, the first electrode layer 447, and the second electrode layer 446and the second substrate 442 are firmly attached to each other with aliquid crystal layer 444 interposed therebetween.

The thin film transistor 422 has a structure in which the semiconductorlayer 403 is in contact with the wiring layers 405 a and 405 b servingas a source electrode layer and a drain electrode layer without an n⁺layer interposed therebetween.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film provided over the thin filmtransistor, the intensity of incident light on the semiconductor layerof the thin film transistor can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistor can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Improvement in contrast and viewing angle characteristics and higherresponse speed enable a liquid crystal display device with higher imagequality and higher performance to be supplied. Further, such a liquidcrystal display device can be manufactured at low cost with highproductivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 7

Another example of a thin film transistor that can be applied to theliquid crystal display devices in Embodiments 1 to 5 will be describedwith reference to FIGS. 9A and 9B.

FIG. 9A is a plan view of a liquid crystal display device illustratingone pixel.

FIG. 9B is a cross-sectional view taken along line Z1-Z2 in FIG. 9A.

In the plan view of FIG. 9A, in a manner similar to that of Embodiment2, a plurality of source wiring layers (including a wiring layer 405 a)are provided in parallel to each other (extended in a vertical directionin the drawing) and apart from each other. A plurality of gate wiringlayers (including a gate electrode layer 401) are provided apart fromeach other and extend in a direction generally perpendicular to thesource wiring layers (a horizontal direction in the drawing). Commonwiring layers 408 are provided adjacent to the plurality of gate wiringlayers and extend in a direction generally parallel to the gate wiringlayers, that is, in a direction generally perpendicular to the sourcewiring layers (a horizontal direction in the drawing). Roughlyrectangular spaces are surrounded by the source wiring layers, thecommon wiring layers 408, and the gate wiring layers, and a pixelelectrode layer and a common wiring layer of a liquid crystal displaydevice are provided in these spaces. A thin film transistor 421 fordriving the pixel electrode layer is provided at the upper left cornerin the drawing. A plurality of pixel electrode layers and thin filmtransistors are provided in matrix.

The first substrate 441 provided with the thin film transistor 421, theinterlayer film 413 which is a light-transmitting chromatic color resinlayer, the first electrode layer 447, and a second electrode layer 446and the second substrate 442 are firmly attached to each other with theliquid crystal layer 444 interposed therebetween.

The thin film transistor 421 is a bottom-gate thin film transistor andincludes, over the first substrate 441 that is a substrate having aninsulating surface, the gate electrode layer 401, the gate insulatinglayer 402, the wiring layers 405 a and 405 b serving as a sourceelectrode layer and a drain electrode layer, the n⁺ layers 404 a and 404b serving as a source region and a drain region, and the semiconductorlayer 403. In addition, the insulating film 407 which covers the thinfilm transistor 421 and is in contact with the semiconductor layer 403is provided. An In—Ga—Zn—O based non-single-crystal film is used for thesemiconductor layer 403 and the n⁺ layers 404 a and 404 b. The thin filmtransistor 421 having such a structure shows characteristics of amobility of 20 cm²/Vs or more and a subthreshold swing (S value) of 0.4V/dec or less. Thus, the thin film transistor can operate at high speed,and a driver circuit (a source driver or a gate driver) such as a shiftregister can be formed over the same substrate as the pixel portion.

It is preferable that reverse sputtering in which an argon gas isintroduced to generate plasma be performed on the gate insulating layer402 and the wiring layers 405 a and 405 b before the formation of thesemiconductor layer 403 by a sputtering method, in order to remove dustattached to surfaces.

The semiconductor layer 403 and the n⁺ layers 404 a and 404 b arepreferably subjected to heat treatment at 200° C. to 600° C., typically300° C. to 500° C. For example, heat treatment is performed for 1 hourat 350° C. in a nitrogen atmosphere. There is no particular limitationon when to perform this heat treatment, as long as it is performed afterthe oxide semiconductor films used for the semiconductor layer 403 andthe n⁺ layers 404 a and 404 b are formed.

In addition, oxygen radical treatment may be performed on thesemiconductor layer 403.

The gate insulating layer 402 exists in the entire region including thethin film transistor 421, and the thin film transistor 421 is providedwith the gate electrode layer 401 between the gate insulating layer 402and the first substrate 441 which is a substrate having an insulatingsurface. The wiring layers 405 a and 405 b and the n⁺ layers 404 a and404 b are provided over the gate insulating layer 402. In addition, thesemiconductor layer 403 is provided over the gate insulating layer 402,the wiring layers 405 a and 405 b, and the n⁺ layers 404 a and 404 b.Although not illustrated, a wiring layer is provided over the gateinsulating layer 402 in addition to the wiring layers 405 a and 405 band the wiring layer extends beyond the perimeter of the semiconductorlayer 403 to the outside.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film provided over the thin filmtransistor, the intensity of incident light on the semiconductor layerof the thin film transistor can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistor can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 8

Another example of a thin film transistor that can be applied to theliquid crystal display devices in Embodiments 1 to 5 will be described.Note that components in common with those in Embodiments 2 to 5 can beformed using a similar material and manufacturing method, and detaileddescription of the same portions and portions having similar functionsis omitted.

An example of a liquid crystal display device including a thin filmtransistor which has a structure in which a source electrode layer and adrain electrode layer are in contact with a semiconductor layer withoutan n⁺ layer interposed therebetween is illustrated in FIGS. 11A and 11B.

FIG. 11A is a plan view of a liquid crystal display device illustratingone pixel. FIG. 11B is a cross-sectional view taken along line Y1-Y2 inFIG. 11A.

In the plan view of FIG. 11A, in a manner similar to that of Embodiment2, a plurality of source wiring layers (including a wiring layer 405 a)are provided in parallel to each other (extended in a vertical directionin the drawing) and apart from each other. A plurality of gate wiringlayers (including a gate electrode layer 401) are provided apart fromeach other and extend in a direction generally perpendicular to thesource wiring layers (a horizontal direction in the drawing). Commonwiring layers 408 are provided adjacent to the plurality of gate wiringlayers and extend in a direction generally parallel to the gate wiringlayers, that is, in a direction generally perpendicular to the sourcewiring layers (a horizontal direction in the drawing). Roughlyrectangular spaces are surrounded by the source wiring layers, thecommon wiring layers 408, and the gate wiring layers, and a pixelelectrode layer and a common wiring layer of a liquid crystal displaydevice are provided in these spaces. A thin film transistor 423 fordriving the pixel electrode layer is provided at the upper left cornerin the drawing. A plurality of pixel electrode layers and thin filmtransistors are provided in matrix.

The first substrate 441 provided with the thin film transistor 423, theinterlayer film 413 which is a light-transmitting chromatic color resinlayer, the first electrode layer 447, and the second electrode layer 446and the second substrate 442 are firmly attached to each other with theliquid crystal layer 444 interposed therebetween.

The gate insulating layer 402 exists in the entire region including thethin film transistor 423, and the thin film transistor 423 is providedwith the gate electrode layer 401 between the gate insulating layer 402and the first substrate 441 which is a substrate having an insulatingsurface. The wiring layers 405 a and 405 b are provided over the gateinsulating layer 402. In addition, the semiconductor layer 403 isprovided over the gate insulating layer 402 and the wiring layers 405 aand 405 b. Although not illustrated, a wiring layer is provided over thegate insulating layer 402 in addition to the wiring layers 405 a and 405b and the wiring layer extends beyond the perimeter of the semiconductorlayer 403 to the outside.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film provided over the thin filmtransistor, the intensity of incident light on the semiconductor layerof the thin film transistor can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistor can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

Improvement in contrast and viewing angle characteristics enables aliquid crystal display device with higher image quality to be supplied.Further, such a liquid crystal display device can be manufactured at lowcost with high productivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 9

A liquid crystal material which exhibits a blue phase can be used forthe liquid crystal layers in the above-described Embodiments. A liquidcrystal display device that uses a liquid crystal layer exhibiting ablue phase will be described with reference to FIGS. 19A to 19D.

FIGS. 19A to 19D are cross-sectional views of the liquid crystal displaydevice and its manufacturing process.

In FIG. 19A, the element layer 203 is formed over the first substrate200 which is an element substrate, and the interlayer film 209 is formedover the element layer 203.

The interlayer film 209 includes the light-transmitting chromatic colorresin layers 204 a, 204 b, and 204 c and the light-blocking layers 205a, 205 b, 205 c, and 205 d. The light-blocking layers 205 a, 205 b, 205c, and 205 d are formed at boundaries of the light-transmittingchromatic color resin layers 204 a, 204 b, and 204 c. Note that thepixel electrode layer and the common electrode layer are omitted inFIGS. 19A to 19D. For example, the pixel electrode layer and the commonelectrode layer can have any of the structures described in Embodiments2 to 8, and a lateral electric field mode can be employed.

As illustrated in FIG. 19B, the first substrate 200 and the secondsubstrate 201 which is a counter substrate are firmly fixed to eachother with the sealants 202 a and 202 b with a liquid crystal layer 206interposed therebetween. As a method for forming the liquid crystallayer 206, a dispenser method (a dropping method) or an injection methodin which after attachment of the first substrate 200 and the secondsubstrate 201, a liquid crystal is injected with the use of capillaryphenomenon can be used.

A liquid crystal material exhibiting a blue phase can be used for theliquid crystal layer 206. The liquid crystal material exhibiting a bluephase has a short response time of 1 msec or less and enables high-speedresponse, whereby the liquid crystal display device can show higherperformance.

The liquid crystal material exhibiting a blue phase includes a liquidcrystal and a chiral agent. The chiral agent is employed to align theliquid crystal in a helical structure and to make the liquid crystal toexhibit a blue phase. For example, a liquid crystal material into whicha chiral agent is mixed at 5 wt % or more may be used for the liquidcrystal layer.

As the liquid crystal, a thermotropic liquid crystal, a low-molecularliquid crystal, a high-molecular liquid crystal, a ferroelectric liquidcrystal, an anti-ferroelectric liquid crystal, or the like is used.

As the chiral agent, a material having a high compatibility with aliquid crystal and a strong twisting power is used. Either one of twoenantiomers, R and S, is used, And a racemic mixture in which R and Sare mixed at 50:50 is not used.

The above liquid crystal material exhibits a cholesteric phase, acholesteric blue phase, a smectic phase, a smectic blue phase, a cubicphase, a chiral nematic phase, an isotropic phase, or the like dependingon conditions.

A cholesteric blue phase and a smectic blue phase, which are bluephases, are seen in a liquid crystal material having a cholesteric phaseor a smectic phase with a relatively short helical pitch of less than orequal to 500 nm. The alignment of the liquid crystal material has adouble twist structure. Having the order of less than or equal to anoptical wavelength, the liquid crystal material is transparent, andoptical modulation action is generated through a change in alignmentorder by voltage application. A blue phase is optically isotropic andthus has no viewing angle dependence. Thus, an alignment film is notnecessarily formed; therefore, display image quality can be improved andcost can be reduced. In addition, rubbing treatment on an alignment filmis unnecessary; accordingly, electrostatic discharge damage caused bythe rubbing treatment can be prevented and defects and damage of theliquid crystal display device can be reduced in the manufacturingprocess. Thus, productivity of the liquid crystal display device can beincreased. A thin film transistor that uses an oxide semiconductor layerparticularly has a possibility that electric characteristics of the thinfilm transistor may fluctuate significantly by the influence of staticelectricity and deviate from the designed range. Therefore, it is moreeffective to use a blue phase liquid crystal material for a liquidcrystal display device including a thin film transistor that uses anoxide semiconductor layer.

The blue phase appears only within a narrow temperature range;therefore, it is preferable that a photocurable resin and aphotopolymerization initiator be added to a liquid crystal material andpolymer stabilization treatment be performed in order to widen thetemperature range. The polymer stabilization treatment is performed insuch a manner that a liquid crystal material including a liquid crystal,a chiral agent, a photocurable resin, and a photopolymerizationinitiator is irradiated with light having a wavelength with which thephotocurable resin and the photopolymerization initiator are reacted.This polymer stabilization treatment may be performed by irradiating aliquid crystal material exhibiting an isotropic phase with light or byirradiating a liquid crystal material exhibiting a blue phase under thecontrol of the temperature with light. For example, the polymerstabilization treatment is performed in the following manner: thetemperature of a liquid crystal layer is controlled and under the statein which the blue phase is exhibited, the liquid crystal layer isirradiated with light. However, the polymer stabilization treatment isnot limited to this manner and may be performed in such a manner that aliquid crystal layer under the state of exhibiting an isotropic phase ata temperature within +10° C., preferably +5° C. of the phase transitiontemperature between the blue phase and the isotropic phase is irradiatedwith light. The phase transition temperature between the blue phase andthe isotropic phase is a temperature at which the phase changes from theblue phase to the isotropic phase when the temperature rises, or atemperature at which the phase changes from the isotropic phase to theblue phase when the temperature decreases. As an example of the polymerstabilization treatment, the following method can be employed: afterheating a liquid crystal layer to the isotropic phase, the temperatureof the liquid crystal layer is gradually decreased so that the phasechanges to the blue phase, and then, irradiation with light is performedwhile the temperature at which the blue phase is exhibited is kept.Alternatively, after the phase changes to the isotropic phase bygradually heating a liquid crystal layer, the liquid crystal layer canbe irradiated with light under a temperature within +10° C., preferably+5° C. of the phase transition temperature between the blue phase andthe isotropic phase (under the state of exhibiting an isotropic phase).In the case of using an ultraviolet curable resin (a UV curable resin)as the photocurable resin included in the liquid crystal material, theliquid crystal layer may be irradiated with ultraviolet rays. Even inthe case where the blue phase is not exhibited, if polymer stabilizationtreatment is performed by irradiation with light under a temperaturewithin +10° C., preferably +5° C. of the phase transition temperaturebetween the blue phase and the isotropic phase (under the state ofexhibiting an isotropic phase), the response time can be made as shortas 1 msec or less and high-speed response is possible.

The photocurable resin may be a monofunctional monomer such as acrylateor methacrylate; a polyfunctional monomer such as diacrylate,triacrylate, dimethacrylate, or trimethacrylate; or a mixture thereof.Further, the photocurable resin may have liquid crystallinity,non-liquid crystallinity, or both of them. A resin which is cured withlight having a wavelength with which the photopolymerization initiatorto be used is reacted may be selected as the photocurable resin, and anultraviolet curable resin can be typically used.

As the photopolymerization initiator, a radical polymerization initiatorwhich generates radicals by light irradiation, an acid generator whichgenerates an acid by light irradiation, or a base generator whichgenerates a base by light irradiation may be used.

Specifically, a mixture of JC-1041XX (produced by Chisso Corporation)and 4-cyano-4′-pentylbiphenyl can be used as the liquid crystalmaterial. ZLI-4572 (produced by Merck Ltd., Japan) can be used as thechiral agent. As the photocurable resin, 2-ethylhexyl acrylate, RM257(produced by Merck Ltd., Japan), or trimethylolpropane triacrylate canbe used. As the photopolymerization initiator,2,2-dimethoxy-2-phenylacetophenone can be used.

The liquid crystal layer 206 is formed using a liquid crystal materialincluding a liquid crystal, a chiral agent, a photocurable resin, and aphotopolymerization initiator.

As illustrated in FIG. 19C, polymer stabilization treatment is performedon the liquid crystal layer 206 by irradiation with light 207, so that aliquid crystal layer 208 is formed. The light 207 is light having awavelength with which the photocurable resin and the photopolymerizationinitiator included in the liquid crystal layer 206 are reacted. By thispolymer stabilization treatment using light irradiation, the temperaturerange in which the liquid crystal layer 208 exhibits a blue phase can bewidened.

In the case where a photocurable resin such as an ultraviolet curableresin is used as a sealant and a liquid crystal layer is formed by adropping method, for example, the sealant may be cured by the lightirradiation step of the polymer stabilization treatment.

When a liquid crystal display device has a structure in which a colorfilter layer and a light-blocking layer are formed over an elementsubstrate as illustrated in FIGS. 19A to 19D, irradiation light from thecounter substrate side is not absorbed or blocked by the color filterlayer and the light-blocking layer; accordingly, the entire region ofthe liquid crystal layer can be uniformly irradiated with the light.Thus, alignment disorder of a liquid crystal due to nonuniformphotopolymerization, display unevenness due to the alignment disorder,and the like can be prevented. In addition, since a thin film transistoris shielded from light by the light-blocking layer, electriccharacteristics of the thin film transistor remains stable.

As illustrated in FIG. 19D, a polarizing plate 210 a is provided on theouter side (a side opposite from the liquid crystal layer 208) of thefirst substrate 200 and a polarizing plate 210 b is provided on theouter side (a side opposite from the liquid crystal layer 208) of thesecond substrate 201. In addition to the polarizing plates, an opticalfilm such as a retardation plate or an anti-reflection film may beprovided. For example, circular polarization may be employed using apolarizing plate or a retardation plate. Through the above-describedprocess, a liquid crystal display device can be completed.

In the case of manufacturing a plurality of liquid crystal displaydevices using a large-sized substrate (a so-called multiple panelmethod), a division step can be performed before the polymerstabilization treatment or before provision of the polarizing plates. Inconsideration of the influence of the division step on the liquidcrystal layer (such as alignment disorder due to force applied in thedivision step), it is preferable that the division step be performedafter the attachment between the first substrate and the secondsubstrate and before the polymer stabilization treatment.

Although not illustrated, a backlight, a sidelight, or the like may beused as a light source. Light from the light source is emitted from theside of the first substrate 200, which is an element substrate, so as topass through the second substrate 201 on the viewer side.

Improvement in contrast and viewing angle characteristics and higherresponse speed enable a liquid crystal display device with higher imagequality and higher performance to be supplied. Further, such a liquidcrystal display device can be manufactured at low cost with highproductivity.

Characteristics of the thin film transistor are stabilized and theliquid crystal display device can have higher reliability.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 10

A thin film transistor is manufactured, and a liquid crystal displaydevice having a display function can be manufactured using the thin filmtransistor in a pixel portion and further in a driver circuit. Further,part or whole of a driver circuit can be formed over the same substrateas a pixel portion, using a thin film transistor, whereby asystem-on-panel can be obtained.

The liquid crystal display device includes a liquid crystal element(also referred to as a liquid crystal display element) as a displayelement.

Further, a liquid crystal display device includes a panel in which adisplay element is sealed, and a module in which an IC or the likeincluding a controller is mounted to the panel. The present inventionfurther relates to one mode of an element substrate before the displayelement is completed in a manufacturing process of the liquid crystaldisplay device, and the element substrate is provided with a means tosupply current to the display element in each of a plurality of pixels.Specifically, the element substrate may be in a state after only a pixelelectrode of the display element is formed, a state after a conductivefilm to be a pixel electrode is formed and before the conductive film isetched to form the pixel electrode, or any of other states.

Note that a liquid crystal display device in this specification means animage display device, a display device, or a light source (including alighting device). Further, the liquid crystal display device includesany of the following modules in its category: a module to which aconnector such as an FPC (flexible printed circuit), TAB (tape automatedbonding) tape, or a TCP (tape carrier package) is attached; a modulehaving a TAB tape or a TCP at the tip of which a printed wiring board isprovided; and a module in which an integrated circuit (IC) is directlymounted on a display element by chip on glass (COG).

The appearance and a cross section of a liquid crystal display panel,which is one embodiment of a liquid crystal display device, will bedescribed with reference to FIGS. 12A1, 12A2, and 12B. FIGS. 12A1 and12A2 are top views of a panel in which highly reliable thin filmtransistors 4010 and 4011 each including an oxide semiconductor film asa semiconductor layer and a liquid crystal element 4013 are sealedbetween a first substrate 4001 and a second substrate 4006 with asealant 4005. FIG. 12B is a cross-sectional view taken along line M-N ofFIGS. 12A1 and 12A2.

The sealant 4005 is provided so as to surround a pixel portion 4002 anda scanning line driver circuit 4004 which are provided over the firstsubstrate 4001. The second substrate 4006 is provided over the pixelportion 4002 and the scanning line driver circuit 4004. Therefore, thepixel portion 4002 and the scanning line driver circuit 4004 are sealedtogether with a liquid crystal layer 4008, by the first substrate 4001,the sealant 4005, and the second substrate 4006.

In FIG. 12A1, a signal line driver circuit 4003 that is formed using asingle crystal semiconductor film or a polycrystalline semiconductorfilm over a substrate separately prepared is mounted in a region that isdifferent from the region surrounded by the sealant 4005 over the firstsubstrate 4001. On the contrary, FIG. 12A2 illustrates an example inwhich part of a signal line driver circuit is formed over the firstsubstrate 4001 with the use of a thin film transistor that uses an oxidesemiconductor. A signal line driver circuit 4003 b is formed over thefirst substrate 4001 and a signal line driver circuit 4003 a that isformed using a single crystal semiconductor film or a polycrystallinesemiconductor film is mounted on the substrate separately prepared.

Note that there is no particular limitation on the connection method ofa driver circuit which is separately formed, and a COG method, a wirebonding method, a TAB method, or the like can be used. FIG. 12A1illustrates an example of mounting the signal line driver circuit 4003by a COG method, and FIG. 12A2 illustrates an example of mounting thesignal line driver circuit 4003 by a TAB method.

The pixel portion 4002 and the scanning line driver circuit 4004provided over the first substrate 4001 include a plurality of thin filmtransistors. FIG. 12B illustrates the thin film transistor 4010 includedin the pixel portion 4002 and the thin film transistor 4011 included inthe scanning line driver circuit 4004. An insulating layer 4020 and aninterlayer film 4021 are provided over the thin film transistors 4010and 4011.

Any of the highly reliable thin film transistors including an oxidesemiconductor film as a semiconductor layer, which are described inEmbodiments 1 to 8, can be used as the thin film transistors 4010 and4011. The thin film transistors 4010 and 4011 are n-channel thin filmtransistors.

A pixel electrode layer 4030 and a common electrode layer 4031 areprovided over the first substrate 4001, and the pixel electrode layer4030 is electrically connected to the thin film transistor 4010. Theliquid crystal element 4013 includes the pixel electrode layer 4030, thecommon electrode layer 4031, and the liquid crystal layer 4008. Notethat a polarizing plate 4032 and a polarizing plate 4033 are provided onthe outer sides of the first substrate 4001 and the second substrate4006, respectively. The pixel electrode layer 4030 and the commonelectrode layer 4031 may have the structure described in Embodiment 1;in such a case, the common electrode layer 4031 may be provided on thesecond substrate 4006 side, and the pixel electrode layer 4030 and thecommon electrode layer 4031 may be stacked with the liquid crystal layer4008 interposed therebetween.

As the first substrate 4001 and the second substrate 4006, glass,plastic, or the like having a light-transmitting property can be used.As plastic, a fiberglass-reinforced plastics (FRP) plate, a polyvinylfluoride (PVF) film, a polyester film, or an acrylic resin film can beused. Further, sheet in which aluminum foil is sandwiched by PVF filmsor polyester films can also be used.

A columnar spacer denoted by reference numeral 4035 is obtained byselective etching of an insulating film and is provided in order tocontrol the thickness (a cell gap) of the liquid crystal layer 4008.Note that a spherical spacer may be used. In the liquid crystal displaydevice that uses the liquid crystal layer 4008, the thickness (the cellgap) of the liquid crystal layer 4008 is preferably about 5 μm to 20 μm.

Although FIGS. 12A1, 12A2, and 12B illustrate examples of transmissiveliquid crystal display devices, an embodiment of the present inventioncan also be applied to a transflective liquid crystal display device.

FIGS. 12A1, 12A2, and 12B illustrate examples of liquid crystal displaydevices in which a polarizing plate is provided on the outer side (theview side) of a pair of substrates; however, the polarizing plates maybe provided on the inner side of the pair of the substrates. Whether thepolarizing plate is provided on the inner side or the outer side may bedetermined as appropriate depending on the material of the polarizingplate and conditions of the manufacturing process. Furthermore, alight-blocking layer serving as a black matrix may be provided.

The interlayer film 4021 is a light-transmitting chromatic color resinlayer and serves as a color filter layer. A light-blocking layer may beincluded in part of the interlayer film 4021. In FIGS. 12A1, 12A2, and12B, a light-blocking layer 4034 is provided on the second substrate4006 side so as to cover the thin film transistors 4010 and 4011. By thelight-blocking layer 4034, contrast can be increased and the thin filmtransistors can be stabilized more.

When a coloring layer of a light-transmitting chromatic color resinlayer is used as the interlayer film 4021 provided over the thin filmtransistors, the intensity of incident light on the semiconductor layersof the thin film transistors can be attenuated without reduction in anaperture ratio of a pixel. Accordingly, electric characteristics of thethin film transistors can be prevented from being varied due tophotosensitivity of the oxide semiconductor and can be stabilized.Further, the light-transmitting chromatic color resin layer can serve asa color filter layer. In the case of providing a color filter layer onthe counter substrate side, precise positional alignment of a pixelregion with an element substrate over which a thin film transistor isformed is difficult and accordingly there is a possibility that imagequality is degraded. Here, since the interlayer film is formed as thecolor filter layer directly on the element substrate side, the formationregion can be controlled more precisely and this structure is adjustableto a pixel with a fine pattern. In addition, one insulating layer canserve as both the interlayer film and the color filter layer, wherebythe process can be simplified and a liquid crystal display device can bemanufactured at low cost.

The thin film transistors may be covered with the insulating layer 4020which serves as a protective film of the thin film transistors; however,there is no particular limitation to such a structure.

Note that the protective film is provided to prevent entry of impuritiesfloating in air, such as an organic substance, a metal substance, ormoisture, and is preferably a dense film. The protective film may beformed by a sputtering method to have a single-layer structure or astacked structure including a silicon oxide film, a silicon nitridefilm, a silicon oxynitride film, a silicon nitride oxide film, analuminum oxide film, an aluminum nitride film, an aluminum oxynitridefilm, and/or an aluminum nitride oxide film.

After the protective film is formed, the semiconductor layer may besubjected to annealing (300° C. to 400° C.).

Further, in the case of further forming a light-transmitting insulatinglayer as a planarizing insulating film, the light-transmittinginsulating layer can be formed using an organic material having heatresistance, such as polyimide, acrylic, benzocyclobutene, polyamide, orepoxy. Other than such organic materials, it is also possible to use alow-dielectric constant material (a low-k material), a siloxane-basedresin, PSG (phosphosilicate glass), BPSG (borophosphosilicate glass), orthe like. The insulating layer may be formed by stacking a plurality ofinsulating films formed of these materials.

A method for forming the insulating layer is not particularly limited,and the following method can be employed in accordance with thematerial: sputtering, an SOG method, spin coating, dip coating, spraycoating, droplet discharging (e.g., ink jetting, screen printing, oroffset printing), doctor knife, roll coating, curtain coating, knifecoating, or the like. In the case where the insulating layer is formedusing a material solution, the semiconductor layer may be annealed (at200° C. to 400° C.) at the same time of a baking step. The baking stepof the insulating layer serves also as the annealing step of thesemiconductor layer, and thereby a liquid crystal display device can bemanufactured efficiently.

The pixel electrode layer 4030 and the common electrode layer 4031 canbe formed using a light-transmitting conductive material such as indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, indium tin oxide (hereinafter referred to asITO), indium zinc oxide, or indium tin oxide to which silicon oxide isadded.

A conductive composition containing a conductive high molecule (alsoreferred to as a conductive polymer) can be used for the pixel electrodelayer 4030 and the common electrode layer 4031.

In addition, a variety of signals and potentials are supplied to thesignal line driver circuit 4003 that is formed separately, and thescanning line driver circuit 4004 or the pixel portion 4002 from an FPC4018.

Further, since the thin film transistor is easily broken by staticelectricity and the like, a protection circuit for protecting the drivercircuit is preferably provided over the same substrate for a gate lineor a source line. The protection circuit is preferably formed using anonlinear element in which an oxide semiconductor is used.

In FIGS. 12A1, 12A2, and 12B, a connection terminal electrode 4015 isformed using the same conductive film as that of the pixel electrodelayer 4030, and a terminal electrode 4016 is formed using the sameconductive film as that of source and drain electrode layers of the thinfilm transistors 4010 and 4011.

The connection terminal electrode 4015 is electrically connected to aterminal included in the FPC 4018 through an anisotropic conductive film4019.

Although FIGS. 12A1, 12A2, and 12B illustrate an example in which thesignal line driver circuit 4003 is formed separately and mounted on thefirst substrate 4001, the present invention is not limited to thisstructure. The scanning line driver circuit may be formed separately andthen mounted, or only a part of the signal line driver circuit or a partof the scanning line driver circuit may be formed separately and thenmounted.

FIG. 16 illustrates an example of a liquid crystal display module whichis formed as a liquid crystal display device disclosed in thisspecification.

FIG. 16 illustrates an example of the liquid crystal display module, inwhich an element substrate 2600 and a counter substrate 2601 areattached to each other with a sealant 2602, and an element layer 2603including a TFT or the like, a display element 2604 including a liquidcrystal layer, and an interlayer film 2605 including alight-transmitting chromatic color resin layer that serves as a colorfilter are provided between the substrates to form a display region. Theinterlayer film 2605 including a light-transmitting chromatic colorresin layer is necessary to perform color display. In the case of theRGB system, respective light-transmitting chromatic color resin layerscorresponding to colors of red, green, and blue are provided forrespective pixels. The polarizing plate 2606 is provided on the outerside of the counter substrate 2601, and a polarizing plate 2607 and adiffuser plate 2613 are provided on the outer side of the elementsubstrate 2600. A light source includes a cold cathode tube 2610 and areflective plate 2611, and a circuit substrate 2612 is connected to awiring circuit portion 2608 of the element substrate 2600 through aflexible wiring board 2609 and includes an external circuit such as acontrol circuit or a power source circuit. As the light source, a whitediode may be used. The polarizing plate and the liquid crystal layer maybe stacked with a retardation plate interposed therebetween.

As the liquid crystal display module to which Embodiment 1 is applied,the following can be used: an MVA (Multi-domain Vertical Alignment)mode, a PVA (Patterned Vertical Alignment) mode, an ASM (AxiallySymmetric aligned Micro-cell) mode, an OCB (Optical CompensatedBirefringence) mode, an FLC (Ferroelectric Liquid Crystal) mode, an AFLC(Anti Ferroelectric Liquid Crystal) mode, or the like.

Through the above process, a highly reliable liquid crystal displaypanel as a liquid crystal display device can be manufactured.

This embodiment can be implemented in combination with any of thestructures disclosed in other embodiments as appropriate.

Embodiment 11

A liquid crystal display device disclosed in this specification can beapplied to a variety of electronic devices (including a game machine).Examples of electronic devices include television sets (also referred toas televisions or television receivers), monitors of computers or thelike, cameras such as digital cameras or digital video cameras, digitalphoto frames, mobile phones (also referred to as cellular phones ormobile phone sets), portable game consoles, portable informationterminals, audio reproducing devices, large-sized game machines such aspachinko machines, and the like.

FIG. 13A illustrates an example of a television set 9600. In thetelevision set 9600, a display portion 9603 is incorporated in a housing9601. Images can be displayed on the display portion 9603. Here, thehousing 9601 is supported by a stand 9605.

The television set 9600 can be operated with an operation switch of thehousing 9601 or a separate remote controller 9610. Channels and volumecan be controlled with an operation key 9609 of the remote controller9610 so that an image displayed on the display portion 9603 can becontrolled. Furthermore, the remote controller 9610 may be provided witha display portion 9607 for displaying data output from the remotecontroller 9610.

Note that the television set 9600 is provided with a receiver, a modem,and the like. With the receiver, a general television broadcast can bereceived. Furthermore, when the television set 9600 is connected to acommunication network by wired or wireless connection via the modem,one-way (from a transmitter to a receiver) or two-way (between atransmitter and a receiver, between receivers, or the like) datacommunication can be performed.

FIG. 13B illustrates an example of a digital photo frame 9700. Forexample, in the digital photo frame 9700, a display portion 9703 isincorporated in a housing 9701. Various images can be displayed on thedisplay portion 9703. For example, the display portion 9703 can displaydata of an image shot by a digital camera or the like to function as anormal photo frame.

Note that the digital photo frame 9700 is provided with an operationportion, an external connection terminal (a USB terminal, a terminalthat can be connected to various cables such as a USB cable, or thelike), a storage medium insertion portion, and the like. Although theymay be provided on the same surface as the display portion, it ispreferable to provide them on the side surface or the back surface forthe design of the digital photo frame 9700. For example, a memorystoring data of an image shot by a digital camera is inserted in therecording medium insertion portion of the digital photo frame, wherebythe image data can be downloaded and displayed on the display portion9703.

The digital photo frame 9700 may have a configuration capable ofwirelessly transmitting and receiving data. Through wirelesscommunication, desired image data can be downloaded to be displayed.

FIG. 14A illustrates a portable game machine including a housing 9881and a housing 9891 which are jointed with a connector 9893 so as to beable to open and close. A display portion 9882 and a display portion9883 are incorporated in the housing 9881 and the housing 9891,respectively. The portable game machine illustrated in FIG. 14Aadditionally includes a speaker portion 9884, a storage medium insertionportion 9886, an LED lamp 9890, an input means (operation keys 9885, aconnection terminal 9887, a sensor 9888 (a sensor having a function ofmeasuring force, displacement, position, speed, acceleration, angularspeed, the number of rotations, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, electric power, radiation, flow rate, humidity, tiltangle, vibration, smell, or infrared ray), a microphone 9889), and thelike. It is needless to say that the structure of the portable gamemachine is not limited to the above and other structures provided withat least a liquid crystal display device disclosed in this specificationmay be employed. The portable game machine may include other accessoryequipments as appropriate. The portable game machine illustrated in FIG.14A has a function of reading out a program or data stored in a storagemedium to display it on the display portion, and a function of sharinginformation with another portable game machine by wirelesscommunication. The portable game machine in FIG. 14A can have variousfunctions without limitation to the above.

FIG. 14B illustrates an example of a slot machine 9900 which is alarge-sized game machine. In the slot machine 9900, a display portion9903 is incorporated in a housing 9901. In addition, the slot machine9900 includes an operation means such as a start lever or a stop switch,a coin slot, a speaker, and the like. It is needless to say that thestructure of the slot machine 9900 is not limited to the above and otherstructures provided with at least a liquid crystal display devicedisclosed in this specification may be employed. The slot machine mayinclude other accessory equipments as appropriate.

FIG. 15A illustrates an example of a mobile phone 1000. The mobile phone1000 is provided with a display portion 1002 incorporated in a housing1001, operation buttons 1003, an external connection port 1004, aspeaker 1005, a microphone 1006, and the like.

When the display portion 1002 of the mobile phone 1000 illustrated inFIG. 15A is touched with a finger or the like, data can be input intothe mobile phone 1000. Furthermore, operations such as making calls andcomposing mails can be performed by touching the display portion 1002with a finger or the like.

There are mainly three screen modes of the display portion 1002. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such as text. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are mixed.

For example, in the case of making a call or composing a mail, a textinput mode mainly for inputting text is selected for the display portion1002 so that text displayed on a screen can be input. In that case, itis preferable to display a keyboard or number buttons on almost all thearea of the screen of the display portion 1002.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone 1000, display on the screen of the display portion 1002 canbe automatically switched by determining the direction of the mobilephone 1000 (whether the mobile phone 1000 is placed horizontally orvertically for a landscape mode or a portrait mode).

The screen mode is switched by touching the display portion 1002 oroperating the operation buttons 1003 of the housing 1001. Alternatively,the screen mode can be switched depending on the kind of imagesdisplayed on the display portion 1002. For example, when a signal of animage displayed on the display portion is of moving image data, thescreen mode is switched to the display mode. When the signal is of textdata, the screen mode is switched to the input mode.

Furthermore, in the input mode, when input by touching the displayportion 1002 is not performed for a certain period while a signal isdetected by the optical sensor in the display portion 1002, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 1002 can also function as an image sensor. Forexample, an image of a palm print, a fingerprint, or the like is takenby touching the display portion 1002 with the palm or the finger,whereby personal authentication can be performed. Furthermore, byproviding a backlight or a sensing light source emitting a near-infraredlight for the display portion, an image of a finger vein, a palm vein,or the like can also be taken.

FIG. 15B also illustrates an example of a mobile phone. The mobile phoneillustrated in FIG. 15B includes a display device 9410 having a displayportion 9412 and operation buttons 9413 in a housing 9411 and acommunication device 9400 having a scan buttons 9402, an external inputterminal 9403, a microphone 9404, a speaker 9405, and a light-emittingportion 9406 which emits light when receiving a call in a housing 9401.The display device 9410 having a display function can be detached fromor attached to the communication device 9400 having a telephone functionin two directions indicated by the arrows. Accordingly, the displaydevice 9410 and the communication device 9400 can be attached to eachother along their short sides or long sides. In addition, when only thedisplay function is needed, the display device 9410 can be detached fromthe communication device 9400 and used alone. Images or inputinformation can be transmitted or received by wireless or wiredcommunication between the communication device 9400 and the displaydevice 9410, each of which has a rechargeable battery.

This application is based on Japanese Patent Application serial no.2008-304243 filed with Japan Patent Office on Nov. 28, 2008, the entirecontents of which are hereby incorporated by reference.

1. (canceled)
 2. A liquid crystal display device comprising: a gatewiring layer; a transistor comprising a semiconductor layer overlappingwith the gate wiring layer; a first insulating film over each of thetransistor and the gate wiring layer; a light-transmitting chromaticcolor resin layer above the first insulating film; a second insulatingfilm above the light-transmitting chromatic color resin layer; a firstelectrode layer above the second insulating film and electricallyconnected to the transistor; a second electrode layer above the secondinsulating film; a liquid crystal layer above each of the firstelectrode layer and the second electrode layer; and a wiring layer belowthe first insulating film and electrically connected to the secondelectrode layer, wherein the light-transmitting chromatic color resinlayer overlaps with the transistor, wherein in a plan view the wiringlayer extends a direction generally parallel to the gate wiring layer,wherein in the plan view the second electrode layer comprises a firstportion generally parallel to the gate wiring layer and a second portionhaving a comb-shape, and wherein in the plan view the first electrodelayer has a comb-shape and comprises a portion overlapping with thewiring layer.
 3. A liquid crystal display device comprising: a gatewiring layer; a transistor comprising a semiconductor layer overlappingwith the gate wiring layer; a first insulating film over each of thetransistor and the gate wiring layer; a light-transmitting chromaticcolor resin layer above the first insulating film; a second insulatingfilm above the light-transmitting chromatic color resin layer; a firstelectrode layer above the second insulating film and electricallyconnected to the transistor; a second electrode layer above the secondinsulating film; a liquid crystal layer above each of the firstelectrode layer and the second electrode layer; and a wiring layer belowthe first insulating film and electrically connected to the secondelectrode layer, wherein the light-transmitting chromatic color resinlayer overlaps with the transistor, wherein in a plan view the firstelectrode layer has a comb-shape, wherein in the plan view the secondelectrode layer comprises a first portion generally parallel to the gatewiring layer and a second portion having a comb-shape, wherein in a planview the wiring layer is generally parallel to the gate wiring layer,and comprises a first portion overlapping with the second electrodelayer and a second portion not overlapping with the second electrodelayer, and wherein the first electrode layer comprises a portionoverlapping with the second portion of the wiring layer.
 4. The liquidcrystal display device according to claim 2, wherein thelight-transmitting chromatic color resin layer comprises two or more ofa red color layer, a green color layer, and a blue color layer.
 5. Theliquid crystal display device according to claim 3, wherein thelight-transmitting chromatic color resin layer comprises two or more ofa red color layer, a green color layer, and a blue color layer.
 6. Aliquid crystal display device comprising: a gate wiring layer; atransistor comprising a semiconductor layer overlapping with the gatewiring layer; a first insulating film over each of the transistor andthe gate wiring layer; a color filter layer above the first insulatingfilm; a second insulating film above the color filter layer; a firstelectrode layer above the second insulating film and electricallyconnected to the transistor; a second electrode layer above the secondinsulating film; a liquid crystal layer above each of the firstelectrode layer and the second electrode layer; and a wiring layer belowthe first insulating film and electrically connected to the secondelectrode layer, wherein the color filter layer overlaps with thetransistor, wherein in a plan view the wiring layer extends a directiongenerally parallel to the gate wiring layer, wherein in the plan viewthe second electrode layer comprises a first portion generally parallelto the gate wiring layer and a second portion having a comb-shape, andwherein in the plan view the first electrode layer has a comb-shape andcomprises a portion overlapping with the wiring layer.
 7. A liquidcrystal display device comprising: a gate wiring layer; a transistorcomprising a semiconductor layer overlapping with the gate wiring layer;a first insulating film over each of the transistor and the gate wiringlayer; a color filter layer above the first insulating film; a secondinsulating film above the color filter layer; a first electrode layerabove the second insulating film and electrically connected to thetransistor; a second electrode layer above the second insulating film; aliquid crystal layer above each of the first electrode layer and thesecond electrode layer; and a wiring layer below the first insulatingfilm and electrically connected to the second electrode layer, whereinthe color filter layer overlaps with the transistor, wherein in a planview the first electrode layer has a comb-shape, wherein in the planview the second electrode layer comprises a first portion generallyparallel to the gate wiring layer and a second portion having acomb-shape, wherein in a plan view the wiring layer is generallyparallel to the gate wiring layer, and comprises a first portionoverlapping with the second electrode layer and a second portion notoverlapping with the second electrode layer, and wherein the firstelectrode layer comprises a portion overlapping with the second portionof the wiring layer.